Conventionally, solder mask resists in the manufacturing of printed wiring boards have been produced by the screen printing of thermosetting or ultraviolet-curing resist inks.
As electronic devices are becoming highly-integrated, higher precision in the wiring and insulation patterns of printed wiring boards is required, and it is difficult to form high precision resist images using the conventional production method of screen printing, due to the occurrence of smears and drips.
Therefore, a method of forming resist images using photolithography has been developed and various inks such as solder resists and marking resists have been improved from the conventional thermosetting type to a photosensitive type capable of image formation.
Furthermore, in the field of electric and electronic materials such as printed wiring boards and semiconductors, materials are required, with the aim of creating a better working environment and protecting the global environment, to be flame-retardant but free from halogen-based compounds and antimony-based compounds which can harm the environment. These requirements also apply to a photosensitive solder mask resist, as one of these electric and electronic materials. However, no photosensitive solder mask resist that is non-halogen-based, non-antimony-based with sufficient flame retardancy has as yet been developed. Therefore, problems have arisen where for example, when a non-halogen-based, non-antimony-based substrate and a solder resist are used in combination to manufacture a non-halogen printed wiring board, the resultant printed wiring board has not met flame retardancy standards because of the inflammability of the solder resist, despite the flame retardancy of the substrate.